Osmunda japonica (syn. Osmunda nipponicaMakino), also called Asian royal fern,[1] is a fern in the genus Osmunda native to east Asia, including Japan, China, Korea, Taiwan, and the far east of Russia on Sakhalin. It is called gobi (고비) in Korean and zenmai (ゼンマイ; 薇) in Japanese.[2]

It is a deciduousherbaceous plant which produces separate fertile and sterile fronds. The sterile fronds are spreading, up to 80–100 cm tall, bipinnate, with pinnae 20–30 cm long and pinnules 4–6 cm long and 1.5–2 cm broad; the fertile fronds are erect and shorter, 20–50 cm tall.

It grows in moist woodlands and can tolerate open sunlight only if in very wet soil. Like other ferns, it has no flowers, but rather elaborate sporangia, that very superficially might suggest a flower, from which the alternative name derives.

In some parts of China (where it is called 蕨菜 or juecai in Mandarin), Tibet and Japan (where it is called zenmai in Japanese), the young frond or fiddlehead of Osmunda japonica is used as a vegetable. In Korea too, these young shoots are commonly used to make dishes like namul.[3]